Problems switching GPUS

I have just installed A new Gtx 660ti to upgrade my old 7850. When I did not remove my old drivers from my system. ( My friend bought my 7850 off me) I removed the amd drivers through the catalyst. I then installed the nvidia drivers and my monitor blacks out after the Starting Windows screen. I can still hear my computer starting up in the background.
I was just wondering if you guys could help me out with this Maybe the catalyst did not uninstall the drivers properly. I have no idea to be honest my PC Specs are

Mobo: M5A99FX Pro r.20

CPU: AMD Fx 8350@4.4 ghz

Ram: G.Skill ribjaws 2x8gb 1600 mhz

PSU; Antec HCG 750W

HDD: Seagate 2tb

SSD: OCZ Vertex 120gb

Monitor: AOC 23.6 inch 2ms
P.S I am using DVI as my connection to the monitor